Manufacture of carbon black



y 1933- E. B. SPEAR El AL MANUFACTURE OF CARBON BLACK 2 Sheets-Sheet 1 Filed Oct. 7, 1925 S R O T N E V N a N gum 4 1925 2 Sheets-Sheet 2 Filed Oct. 7,

INVENTORS NW2. A, W U Ml Patented May 23, 1933 i UNITED STATES PATENT OFFICE ELLWOOD B. SPEAB, O]? PITTSBURGH, AND ROBERT L. HOORE, OF DOBHONT, PENNSYL- VANIA, ABSIGNORS TO THEBMATOMIC CA RBON COMPANY, OF PITTSBURGH, PENN- BYLVANIA, A. CORPORATION OF DELAWARE MANUFACTURE OF CARBON BLACK Application filed October 7, 1925. Serial No. 61,149.

The present invention relates to the manufacture of carbon black. Carbon black is a well known article of commerce and is used extensively as a pigment, as a filler for rubber compounding, and so forth. Carbon black has, until recent years, been produced almostexclusively by burning gas, such as natural gas, in a smoky flame against a cool metal surface upon which the carbon black was deposited and subsequently scraped off. The carbon black thus produced, andordinarily known as channel black, is a fine, flufiy jet black powder composed of minute particles of carbon. Carbon black has also been made, in recent years, by burning a gas, such as natural gas, with an insufiicient supply of air and collecting the soot-like carbon black produced by the incomplete combustion of the gas. Carbon black has also been produced by passing a gas, such as natural gas, through a highly preheated checkerwork retort in which the gas is thermally broken down to form carbon black which is separatedjfrom the gaseous stream as described, for example, in the Brownlee and Uhlinger Patent No. 1,520,115 of December 23, 1924.- The carbon thus produced is described inthe Brownlee and Uhlinger Patent No. 1,473,730 of Dec. 25, 1923 and is of a greater weight per unit volume than ordinary channel carbon black and has a grayish color. The greater weight and grayish color are apparently due to the greaterlength of time that the carbon remains in the heated retort. The carbon produced upon the initial decomposition of the gas has apparently the jet black color and other characteristics of the channel carbon black, but is converted into the grayish carbon of greater weight during the period of from 15 to 20 seconds that it remains in the heated retort before passing out to the cooling and collecting devices.

The yield of carbon made by the Brownlee and Uhlinger process is greater than by the usual process of making channel black. but the color has been objectionable for some uses.

In the process which we are about to describe the color of the carbon block may be of the usual commercial channel black may be produced and with a yield comparable to that of the Brownlee and Uhlinger process. Other characteristics of the carbon, particularly its effect when combined with rubber, may be varied by modifying our process as hereinafter described. Also, relatively pure hydrogen may be secured as a by-product if desired. Such hydrogen is a valuable byproduct and may be used in the production of synthetic ammonia and fertilizers.

In carrying out the process, the gas, usually natural gas, is mixed with a preheated diluent gas, preferably hydro en, which is preferably the hydrogen which remains after the carbon is removed from the natural gas and a portion of which is re-cireulated as the diluent gas. The mixture of the hydrocarbon gas and diluent gas is further heated, preferably by passing through checkerwork or other heating means which may be burned out from time to time to remove deposited carbon. The hydrocarbon breaks down yielding carbon black which is rapidly swept through the reaction zone and may thus be obtained with a jet black color characteristic of the ordinary channel black.

In the drawings:

Figure 1 is an elevation taken partly in vertical section, showing more or less diagrammatically the preferred apparatus for carrying out the process.

Figure '2 is a vertical section through the heating retort; and

Figure 3 is a vertical section through a heating retort showing a modification.

Referring to the illustrated embodiment of i the invention, reference numeral 1 indicates the heating retort in which the diluent gas is preheated and in which the decomposition of the hydrocarbon gas takes place. The gas which has been decomposed in the retort, and which consists principally of hydrogen with entrained carbon particles, passes through the outlet 2 into a chamber 3 into which water sprays 4 discharge to cool the gas. The gas is highly heated and converts the water into steam, the latent heat of evaporation serving to efiiciently 7 cool the gas. The gas then passes downwardly through a column 5 and along a. conveyor passage 6 into the main separating chamber 7 where the gas passes through the fabric bags 8 which are shaken from time to time to dislodge the carbon. The carbon from the separator 7 and tower 5 falls into the conveyor passage 6 where it is pushed along to the right, as viewed in Figure 1, by means of the screw conveyor 9, to a bin, from which it is bagged. The gas from which the entrained carbon particles have been removed goes from the separator 7 into a discharge pipe 10 having two branches 11 and 12. The branch 11 leads back to the retort 1 through which the hydrogen gas may be recirculated. The brahch 12 leads the excess hydrogen off where it may be utilized for any desired purpose, such as in the manufacture of ammonia, fertilizers, etc. The pipe 11 is preferably provided with a blower 13 for handling the hydrogen gas.

The above is a general description of the layout of the apparatus. The retort 1 and the reactions taking place therein will now be described in more detail.

The retort 1 has a steel casing 14 with a refractory heat insulating lining 15 preferably of tirebrick. The chamber within the retort is tilled, for the most part, with checkerwork 16 made of refractory brick. The checkerwork may be considered as divided into three parts or zones. First, the zone A, in which the diluent gas is preheated; second, the zone B, in which the hydrocarbon gas is preheated, and third, the zone C or reaction zone, in which the mixture of hydrocarbon gas and diluent gas is further heated and in which the hydrocarbon gas is decomposed.

The checkerwork constituting the zone B is formed in a lateral extension or pocket 17 of the retort. This heating zone may be omitted if desired, in which case the hydrocarbon gas is not preheated, as shown in Figure 3. The retort shown in Figure 3 is the same as that in Figure 2 but with the omission of the brickwork forming the gas preheating zone B.

The retort is provided with suitable connections for admitting and discharging the gases and products of combustion. The top of the retort is provided with a large discharge passage or chimney 18 throughwhich the products of combustion are discharged during the heating blast. The opening 18 is closed by a stop valve 19 which discharges into a hood 20 through a stack 21 through the roof of the building. Two inlet pipes 22 ententhe sides of the opening 18 to admit the diluent gas, or diluent gas mixed with air, if desired. The pipes 22 are connected through the valves 23 to the pipe 11, through which the hydrogen is drawn from the separator 7. Branch pipes 24 provided with valves 25 en ter the pipes 22 and permit the introduction of air or other gas to be mixed with the hydrogen.

The hydrogen gas to be decomposed, which is usually natural gas, is admitted to the preheating zone B through pipe 26 provided with a controlling valve27. A branch pipe 28 provided with a valve 29 enters the pipe 26 and permits the introduction of air or other gas to be mixed with the hydrocarbon gas before it passes into the heating zone B. At the bottom of the retort is an inlet pipe 30 through which is forced a mixture of air and gas for the purpose of applying a heating blast to the checkerwork intermit: tently and to burn out accumulated carbon deposits. The gas used for this purpose may be natural gas, or the excess hydrocarbon, or producer or other fuel gas. The supply of gas and air may be regulated by the valves 31 and 32 in the branch pipes leading to the inlet pipe 30.

The outlet passage 2 has a gate valve 33 which is closed when the heating blast is applied to the retort.

The upper checkerwork forming the diluent gas pre-heating zone A is separated from the lower checkerwork C by a relatively unobstructed zone 34 into which the hydrocarbon gas is discharged to mingle with the downwardly flowing diluent gas. The check: erwork forming the reaction zone C is supported on columns to leave another relatively unobstructed space 35 at the bottom of the retort from which the gas flows to the outlet passage 2.

The operation of the apparatus is as follows :The checkerwork is first heated by applying a heating blast. During the blast the valves 23, 24 and 33 are closed to shut 011' the retort from the carbon collecting portion of the apparatus. The valves 31 and 32 are opened to admit a combustible mixture of gas through the pipe 30 to the bottom of the retort. The valves 27 and 29 are also opened to admit a smaller quantity of the combustible mixture to the eheckerwork zone B in the retort in which such checkerwork is employed. The valve 19 is opened wide to allow the gases of combustion to pass off into the stack 21. The heating blast is maintained until the checkerwork is heated to the desired temperature. The eheckerwork in the zone C is heated to a preferred temperature of about 1200 to 1400 C. The lower portion of the checkerwork zone A is heated to about this same temperature, although the upper por tion of the zone A need not be heated to as high temperature. The gas admitted to heat the eheckerwork zone B is regulated so that the checkerwork is heated to a temperature somewhat below the decomposition point of the hydrocarbon, preferably about 700 or 800 C. The temperature of the zone B may be prevented from rising above this temperature by forcing in an excess of cold air through the inlet pipe 26.

After the temperature in the three zones of the retort have reached the desired points, the blast is shut off and the discharge valve 19 closed. The valve 33 is then opened and the valves controlling the pi s 22 and 26 are also opened to introduce t e diluent gas and the hydrocarbon gas. If the valves 23 and 27 are opened hydrogen, as the diluent :15, is forced into the top of the retort and ows down through the heating zone A and the hydrocarbon gas, preferably natural gas, is introduced through the pipe 26 and through the heating zone B in the form of retort shown in Figure 2. The hydrocarbon gas is preheated in the zone B to a point slightly below its decomposition temperature. The diluent gas flowing down throu h the heating zone A is, however, highly pre eated to a temperature well above the decomposition temperature of the hydrocarbon gas. The hydrocarbon gas and diluent gas mix in the space 34 and the mixture passes downward through the reaction zone C, where the mixture is still further heated by the checkerwork C. When the hydrocarbon gas meets the highly preheated diluent gas, decomposition of the hydrocarbon gas into solid carbon particles and hydro en begins, and this is further augmented by the additional heat supplied by the highly heated checkerwork C. During the passage of the mixture through the checkerwork zone C, some of the particles of the solid carbon come in contact with the checkerwork and become encrusted thereon. The remainder of the carbon, however, passes along with the current of gas and out through the discharge passage 2 and into the collecting apparatus, where it is separated from the gas. The volume of diluent gas is preferably several times that of the hydrocarbon gas, usually somewhere in the neighborhood of five volumes of diluent gas to one volume of hydrocarbon gas. The relatively large volume of diluent gassweeps the mixture rapidly through the reaction zone C so that -the carbon particles are not allowed to remain in this highly heated zone for but a very few seconds and the carbon black retains its jet black appearance and the graying of the carbon is prevented. The use of diluent gas also serves to desirably decrease the size of the carbon particles formed. When the hydrocarbon as is diluted, there will be a greater num r of condensation centers for a given wei ht of the resultant carbon and therefore t e carbon particles will be smaller and a more valuable product obtained. The hydrocarbon passing through the heating zone B must not be heated above its decomposition temperature, otherwise the carbon will be deposited on the brickwork and undesirable intermediate products of a tarry nature will be formed. It is found, however, that the sudden heating of the hydrocarbon by its contact with the highly preheated diluent gas, together with thesudden heating to which the mixture is immediately exposed in its passage through the checkerwork zone C, greatly reduces or entirely eliminates the formation of undesirable tarry or oily products which might contaminate the collected carbon black.

As above noted, during the passage of the mixture through the checkerwork zone C, particles of solid carbon come in contact with the checkerwork and become encrusted thereon. In order to clean the checkerwork, a lean mixture of air and gas is forced through the pipe 30 during the blast so as to burn the encrusted carbon off the checkerwork of zone C, thus preventing the checkerwork from becoming clogged and also utilizing the fuel value of this carbon for heating the retort.

The character of the carbon may be controlled by varying the time of passage of the h drocarbon gas through the reaction zone (5 By usin a relatively large volume of diluent gas t e mixture may be swept rapidly throu h the reaction zone C and the jet black fluii y characteristics of the channel carbon black are retained. By using less diluent gas, or by lengthening the reaction zone C, the carbon black may be given more of the properties of thermatomic carbon, namely, a greater weight per unit volume and a tendency to a rayish color. The process, therefore, permits the variation in the character of carbon black produced.

Recirculated hydrogen is preferred as the diluent gas, since it is inert, and by the term inert diluent gas we mean a diluent gas which will not chemically combine with the hydrocarbon gas to any substantial extent, as by combustion. However, other inert diluent gases, such as nitrogen or carbon dioxide, may be used, or gases such as air may be used as the diluent. The hydrogen, however, is preferred, since it is a by-product from the process. Moreover, the gas as it leaves the retort is not entirely decomposed, and while it consists principally of hydrogen, it usually contains a small amount of undecomposed hydrocarbon gas. When this gas is a ain recirculated as a diluent gas the residual undecomposed hydrocarbon gas again goes through the retor and is further decomposed, thus giving t e maximum recovery from the original gas.

In the form of retort shown in Figure 2 the hydrocarbon gas is reheated to a point just below its decomposition temperature by the checkerwork of the heating zone B, while in the form of retort shown in F igure 3 the hydrocarbon gas is introduced without preheating into the diluent gas. The apparatus may be operated satisfactorily in either way, particularly where a large volume of diluent gas is used, since the highly preheated diluent gas .will raise the cold hydrocarbon gas er process.

above its decomposition temperature and the heating will be further augmented by the checkerwork zone C. The hydrocarbon gas, moreover, may be preheated by some partial combustion if air is bled into the gas through the branch pipe 28.

The partial combustion caused by the introduction of air serves to quickl raise the temperature and tends to still urther prevent or minimize the production of tarry or oily matter and other undesirable substances which might otherwise contaminate the collected carbon black.

'hen the hydrogen is subsequently used, as for example, in the manufacture of synthetic ammonia or fertilizers, it is desirable that it should be as free as possible from eontaniinating gases, such as carbon dioxide and carbon monoxide. Under such conditions it is, therefore, desirable to use hydrogen alone as the diluent gas. However, under some conditions it may be desirable to bleed in a certain amount of air. This may be done by admitting air through the branch pipes 24 to be mixed with the diluent gas entering the retort. Or air may be introduced through the branch pipe 28 to mix with the hydrocarbon gas entering through the inlet pipe 26. When air is admitted, combustion takes place, increasing the temperature of the gases and retarding the chilling of the checkerwork by the mixture of the air and hydrogen, or the mixture of the air and byd rocarbon gas.

\Vhen air is admitted, oxygen combines with the hydrogen or with the hydrocarbon gas to form superheated steam. This steam has a marked influence upon certain properties of the c arbon black. It apparently serves to bi rn out the hydrocarbons present in the carbon thus activating the carbon. The degree of activation can be controlled by the amount of steam produced by the bleed ing in of the air.

The carbon produced with air bleeding has a much greater stiffening effect when combined with rubber than the carbon black produced by the Brownlee and Uhling- Its rubber-stifiening qualities are comparable with those of ordinary commercial carbon black, but may be controlled since the rubber-stiffening qualities are apparently dependent upon the degree of activation of the carbon. The carbon black produced without the bleeding in of air has rubber-stitl'ening qualities comparable with the carbon black of the Brownlee and Uhlinger process and may be employed to advan tage for soft stock, such as frictions for belts and pneumatic tires.

Other modifications may be made in the process. For example, when the gaseous decomposition products of the hydrocarbon gas are used as the diluent gas, the checkerwork zone C may be made much smaller or entirely eliminated. In this case a relatively large volume of the diluent gas is highly preheated and furnishes suflicient heat for a substantial decomposition of the hydrocarbon gas which is mixed with it, the hydrocarbon gas being also preferably preheated to just below its decomposition point. The decomposition gases are readily available in sufficient quantities to furnish the volume of preheated gas necessary to decompose the hydrocarbon gas. Moreover, any undecomposed hydrocarbon gas in the re-circulated diluent gas is again ex osed to the heat in the retort. This modi ed process may be carried out in the retort shown by introducing the hydrocarbon gas at the very bottom of the retort, as, for example, through the pipe 30, and utilizing all of the brick work within the body of the retort for preheating the re-circulated diluent gas. Or, if desired, the checkerwork below the pipe 26 through which hydrocarbon gas is introduced may be taken out and the space thus provided below the heating zone A utilized as the mixing and reactionchamber in which the decomposition of the hydrocarbon gas takes place.

Another modification of the process and one which has been found to produce an excellent grade of carbon is the mixing of the diluent gas and the hydrocarbon before they are heated. In carrying out such process, instead of admitting the h drocarbon gas through the pipe 26, it may e admitted into the top of the retort through the pipes 22 by means of branch inlet as supplying pipes 36 controlled by valves 3 In this case the hydrocarbon gas and diluent gas are mixed before they pass to the heated checkerwork of the retort. Decomposition in this case begins to take place at the top of the zone A and continues as the gases pass downward through the retort. The diluent gas which is mixed with the hydrocarbon gas is preferably the gaseous products of decomposition from previously treated hydrocarbon gas. However, air may be added along with such decomposition products, or air alone may be used as the diluent gas to be mixed with the hydrocarbon gas before they are heated to decompose the hydrocarbon gas. In case air is used, the supply must be limited so that only a limited partial combustion can take place. While the air tends to burn u some of the gas, it has an advantage in ten ing to raise the temperature of the cold mixture by partial combustion before the mixture passes into the hot checkerwork, thus preventing rapid chilling of the checker. The process gives a large production of carbon from the hydrocarbon gas, such as natural gas, and at the same time permits the control of the character of the carbon black produced, yielding carbon black of the desired quality. The apparatus is economical to operate, the heat losses are reduced to the minimum, and the clogging of the p P and checkerwork is prevented.

' While we have described the preferred embodiment of our invention in considerable detail, it is to be understood that the invention is not limited to its preferrred and described embodiments, but may be otherwise embodied within the scope of the following claim.

We claim: Afiparatus for the production of carbon blac comprisin a retort having a chamber containing ree zones of refractory checker work, means for periodically applying a heating blast to heat the several zones of checker work, means for p a diluent gas through the first zone, means or passin the hydrocarbon gas to be decompose through the second zone and for mixing the thus preheated gases and for passing the mixture through the third zone to further heat the mixture, whereby the hydrocarbon gas is decomposed into gaseous decomposition products and solid carbon articles, and means for separating the car on articles from the gaseous decom osition pr note.

In testimony whereo? we have hereunto set our hands.

ELLWOOD .B. SPEAR. ROBERT L. MOORE.

CERTIFICATE OF CORRECTION.

Patent No. 1,911,003. May 23, 1933.

ELLWOOD B. .SPEAR, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 66, for "hydrogen" read "hydrocarbon"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this Zflld day of August, A. D. 1933.

M. J. Moore.

( Acting Commissioner of Patents.

minimum, and the clogging of the p P and checkerwork is prevented.

' While we have described the preferred embodiment of our invention in considerable detail, it is to be understood that the invention is not limited to its preferrred and described embodiments, but may be otherwise embodied within the scope of the following claim.

We claim: Afiparatus for the production of carbon blac comprisin a retort having a chamber containing ree zones of refractory checker work, means for periodically applying a heating blast to heat the several zones of checker work, means for p a diluent gas through the first zone, means or passin the hydrocarbon gas to be decompose through the second zone and for mixing the thus preheated gases and for passing the mixture through the third zone to further heat the mixture, whereby the hydrocarbon gas is decomposed into gaseous decomposition products and solid carbon articles, and means for separating the car on articles from the gaseous decom osition pr note.

In testimony whereo? we have hereunto set our hands.

ELLWOOD .B. SPEAR. ROBERT L. MOORE.

CERTIFICATE OF CORRECTION.

Patent No. 1,911,003. May 23, 1933.

ELLWOOD B. .SPEAR, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 66, for "hydrogen" read "hydrocarbon"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this Zflld day of August, A. D. 1933.

M. J. Moore.

( Acting Commissioner of Patents. 

